Platinum core-shell structures are used as a catalyst at both electrodes in fuel cells. a. In no more than 50 words, explain the purpose of catalyst in a fuel cell. (2 marks) b. Explain what a core-shell structure is and give one advantage of using core-shell nanostructures as the catalyst in fuel cells. (1 mark) c. You have been tasked to fabricate a core-shell structure for a Pt shell which is a few (3 4) atomic layers thick. i. Which type of growth technique will you suggest for fabricating the core-shell structure and why? ii. What condition must be met to ensure uniform Pt shell growth? (2 marks)